Plate material cutting method, printed circuit board, and electronic device

ABSTRACT

According to one embodiment, a plate material cutting method prepares a plate material including a joining member that joins a main body portion to a throw-out portion, sets the plate material on a die including an opening section, and pushes a punch against the joining member. The punch includes a first end portion corresponding to a first end of the joining member which is connected to the main body portion. The punch also includes a second end portion corresponding to a second end of the joining member which is connected to the throw-out portion. A gap smaller than thickness of the plate material is defined between the first end portion of the punch and an inner surface of the opening section. A gap larger than the thickness of the plate material is defined between the second end portion of the punch and the inner surface of the opening section.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2005-288005, filed Sep. 30, 2005, theentire contents of which are incorporated herein by reference.

BACKGROUND

1. Field

One embodiment of the invention relates to a plate material cuttingmethod, a printed circuit board, and an electronic device. For example,one embodiment of the invention relates to (i) a plate material cuttingmethod which is used for cutting a plate material to obtain a member,and (ii) a printed circuit board and an electronic device provided witha member which is cut out from the plate material.

2. Description of the Related Art

An electronic device such as a hard disk drive (hereinafter referred toas HDD) is provided with a printed circuit board. The printed circuitboard can be prepared in a variety of methods. For example, a thincircuit board such as a flexible printed circuit board is made bypress-working a sheet-like metal plate.

To make a printed circuit board, a sheet-like metal plate is cut out tohave a predetermined product shape. By this working, the metal plate isdivided into main body portion which is used as part of a product, and athrow-out portion which is later thrown out. A joining member isprovided between the main body portion and the throw-out portion toconnect these portions together. In other words, the main body portionis not completely cut off from the throw-out portion; it is supported bythe throw-out portion, with the joining member located in between.

A circuit component is mounted on the main body portion in the statewhere the main body portion is supported by the throw-out portion. Afterthe circuit component is mounted, the main body portion is separatedfrom the joining member. In this manner, the main body portion isseparated completely from the throw-out portion, and the printed circuitboard can be mounted on an electronic device.

The main body portion is separated from the joining member by use of adie assembly including: a punch; a die having an opening sectioncorresponding to the punch; and a blank holder. In the die assembly, thegap between the outer surface of the punch and the inner surface of theopening section is less than the thickness of a workpiece.

A metal plate is set on the die assembly in such a manner that thejoining member is located above the opening section. With the metalplate secured to the die assembly, the punch is forcibly pushed againstthe joining member. By pushing the punch against the joining member, ashearing force is applied to the boundary between the main body portionand the joining member and to the boundary between the throw-out portionand the joining member. As a result, both the boundary between the mainbody portion and the joining member and the boundary between thethrow-out portion and the joining member are cut.

A method for separating the main body portion from the throw-outportion, a cap manufacturing method is proposed, which separates a capmember from a throw-out member. An example of such a cap manufacturingmethod is described in Jpn. Pat. Appln. KOKAI Publication No. 11-114635,for example. The cap member described in this KOKAI Publication No.11-114635 is supported by a throw-out portion by means of a joiningmember. By cutting the joining member by means of a blade cutter, thecap member is separated from the throw-out portion.

In the case of a small-sized HDD, a printed circuit board is very small.Therefore, a joining member which joints the main body portion of theprinted circuit board to the throw-out portion is much smaller andlighter in weight.

The die assembly is so designed as to drop the cutoff joining memberfrom the die assembly as a waste. In other words, the cutoff joiningmember does not impede the subsequent manufacturing process. However, ifthe joining member is too light in weight, it does not fall from the dieassembly and may adhere to the surface of the punch, die or blankholder. If the press working is continued, with the joining memberadhered to the surface of the punch, die or blank holder, the productmay have an indentation resulting from the joining member.

In the manufacturing method described in Jpn. Pat. Appln. KOKAIPublication No. 11-114635, the joining member is cut off by means of ablade cutter. The blade cutter may be useful where portions to be cut isdisposed in line, but is not advantageously applied to the case where aplurality of joining members extend in various directions.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

A general architecture that implements the various feature of theinvention will now be described with reference to the drawings. Thedrawings and the associated descriptions are provided to illustrateembodiments of the invention and not to limit the scope of theinvention.

FIG. 1 is an exemplary perspective view of a cellular phone according toa first embodiment of the invention;

FIG. 2 is an exemplary perspective view of an HDD according to the firstembodiment;

FIG. 3 is an exemplary exploded perspective view of the HDD of the firstembodiment;

FIG. 4 is an exemplary plan view of a metallic plate used in the firstembodiment;

FIG. 5 is an exemplary sectional view of a press working apparatusaccording to the first embodiment;

FIG. 6 is an exemplary perspective view showing how a punch and a dieare related in the first embodiment;

FIG. 7 is an exemplary plan view showing how the punch and the die arerelated in the first embodiment;

FIG. 8 is an exemplary sectional view showing how the metallic plate ofthe first embodiment is before it is punched;

FIG. 9 is an exemplary sectional view showing how the metallic plate ofthe first embodiment is when it is being punched;

FIG. 10 is an exemplary sectional view showing how the metallic plate ofthe first embodiment is after it is punched;

FIG. 11 is an exemplary perspective view showing how the punch and dieof a press working apparatus according to the second embodiment of thepresent invention are related;

FIG. 12 is an exemplary plan view showing how the punch and die of thesecond embodiment are related; and

FIG. 13 is an exemplary sectional view of a die according to anotherembodiment of the invention.

DETAILED DESCRIPTION

Various embodiments according to the invention will be describedhereinafter with reference to the accompanying drawings. In general,according to one embodiment of the invention, a plate material cuttingmethod according to one aspect of the present invention prepares a platematerial including a main body portion, a throw-out portion and ajoining member that joins the main body portion to the throw-outportion. The plate material is set on a die including an opening sectionin such a manner that the joining member is opposed to the openingsection. In this state, a punch opposing the opening section is pushedagainst the joining member. The punch includes a first end portioncorresponding to that end of the joining member which is connected tothe main body portion, and a gap smaller than thickness of the platematerial is defined between the first end portion of the punch and aninner surface of the opening section. The punch also includes a secondend portion corresponding to that end of the joining member which isconnected to the throw-out portion, and a gap larger than the thicknessof the plate material is defined between the second end portion of thepunch and the inner surface of the opening section.

In general, according to one embodiment of the invention, a printedcircuit board according to another aspect of the present inventionprovided with a main body portion and a circuit component mounted on themain body portion. The main body portion is prepared from a platematerial by use of a punch and a die including an opening sectioncorresponding to the punch. The plate material includes the main bodyportion, a throw-out portion and a flexible joining member that joinsthe main body portion to the throw-out portion. The punch includes afirst end portion and a second end portion. When the plate material isset on the die, the first end portion of the punch corresponds to thatend of the joining member which is connected to the main body portion,and the second end portion of the punch corresponds to that end of thejoining member which is connected to the throw-out portion. A gapsmaller than thickness of the plate material is defined between thefirst end portion of the punch and an inner surface of the openingsection. A gap larger than the thickness of the plate material isdefined between the second end portion of the punch and the innersurface of the opening section.

In general, according to one embodiment of the invention, an electronicdevice according to a further aspect of the invention provided with acasing and a printed circuit board received in the casing. The printedcircuit board includes a main body portion and a circuit componentmounted on the main body portion. The main body portion is prepared froma plate material by use of a punch and a die including an openingsection corresponding to the punch. The plate material includes the mainbody portion, a throw-out portion and a flexible joining member thatjoins the main body portion to the throw-out portion. The punch includesa first end portion and a second end portion. When the plate material isset on the die, the first end portion of the punch corresponds to thatend of the joining member which is connected to the main body portion,and the second end portion of the punch corresponds to that end of thejoining member which is connected to the throw-out portion. A gapsmaller than thickness of the plate material is defined between thefirst end portion of the punch and an inner surface of the openingsection. A gap larger than the thickness of the plate material isdefined between the second end portion of the punch and the innersurface of the opening section.

An embodiment of the present invention will now be described, referringto the case where the present invention is applied to a cellular phone.

FIGS. 1-10 show a cellular phone, which is an example of an electronicdevice according to the first embodiment of the present invention. Asshown in FIG. 1, the cellular phone 1 includes a main body 2, a displayunit 3 and a hinge portion 4.

The main body 2 includes a box-like casing 5. The casing has an upperwall on which a plurality of push-type operation keys 6 are arranged.The casing 5 contains a main board 7 and an HDD 8. The display unit 3includes a display housing 9 and a liquid crystal display module 10received inside the display housing 9. The liquid crystal display module10 has a display screen 10 a. The display screen 10 a is exposed to theoutside of the display housing 9 though an opening section 9 a of thedisplay housing 9. The display unit 3 is supported by the rear endportion of the main body 2 by means of the hinge portion 4.

The HDD 8 received in the casing 5 of the main body 2 is an example of adisk drive, which is one type of electronic device. As shown in FIG. 2,the HDD 8 includes an HDD main body 11 and a circuit board unit 12. Forexample, the length L of the HDD main body 11 is 32 mm and the width Wthereof is 24 mm. The total thickness T of the HDD main body 11 and thecircuit board unit 12 combined is in the range of 3 mm to 6 mm.

As shown in FIG. 3, the circuit board unit 12 is attached to the HDDmain body 11 from below. The circuit board unit 12 includes a controlcircuit board 14 and an interface board 15. The control circuit board 14is electrically connected to the HDD main body 11 and controls the same.The interface board 15 has one end portion electrically connected to thecontrol circuit board 14, and the other end portion electricallyconnected to the main board 7 of the cellular phone 1.

The HDD main body 11 has a case 17. The case 17 is shaped like a box andhas an upper wall 17 a, a lower wall 17 b and side walls 17 c. As shownin FIG. 3, the case 17 contains a magnetic disk 21, a spindle motor 22,a magnetic head 23, a head actuator 24, a voice coil motor 25 and asignal processing section 26.

The magnetic disk 21 is an example of a disk-shaped informationrecording medium. The magnetic disk 21 has a diameter of 0.85 inches,for example. The spindle motor 22 is attached to the lower wall 17 b.The spindle motor 22 includes a rotatably-supported hub 22 a. Themagnetic disk 21 is concentrically fitted around the hub 22 a.

As shown in FIG. 3, the head actuator 24 includes a bearing portion 24 aand an arm portion 24 b horizontally extending from the bearing portion24 a. The tip end of the arm portion 24 b supports the magnetic head 23.The magnetic head 23 writes information on the magnetic disk 21 andreads information from the magnetic disk 21. The bearing portion 24 arotatably supports the arm portion 24 b. Thus, the magnetic head 23 ismovable between an operating position where it is on the surface of themagnetic disk 21 and a retreat position where it is located away fromthe magnetic disk 21. The voice coil motor 25 rotates the head actuator24.

As shown in FIG. 3, the signal processing section 26 includes a printedcircuit board 28 and a connector 29. The connector 29 is attached to thelower surface of the printed circuit board 28. The connector 29 isfitted in a hole (not shown) formed in the lower wall 17 b of the case17 and exposed to the outside of the case 17. The connector 29 iselectrically connected to the control circuit board 14 of the circuitboard unit 12.

An example of the printed circuit bard is made of flexible printedcircuit board (herein after referred to as an FPC). The printed circuitboard 28 includes a printed wiring board 31 and a circuit component 32mounted on the printed wiring board 31. The printed wiring board 31 isan example of the main body portion. The printed wiring board 31includes a board main body 31 a and a connection portion 31 b.

The board main body 31 a is secured to the lower wall 17 b in the foldedstate. The connection portion 31 b is integral with the board main body31 a. The connection portion 31 b extends along the side surface of theboard main body 31 a. The distal end of the connection portion 31 b isconnected to the head actuator 24. To be more specific, the connectionportion 31 b is electrically connected to the magnetic head 23 by way ofa cable (not shown) provided on the head actuator 24. With thisconfiguration, the signal processing section 26 sends signals related toinformation processing to the magnetic head 23. An example of thecircuit component 32 is a head IC, a head amplifier or the like.

FIG. 4 shows the printed circuit board 28 which is in the state of beingfabricated. As shown in FIG. 4, a plurality of printed wiring boards 31are formed in one metallic plate 34. In other words, the sheet-likemetallic plate 34 is subject to press working in such a manner thatouter shapes of desired printed wiring boards 31 are punched out.

The metallic plate 34 is an example of the plate material. The metallicplate 34 is a very thin plate of stainless steel and is flexible. Asshown in FIG. 4, the metallic plate 34 includes printed wiring boards31, a throw-out portion 36 and joining members 37. The throw-out portion36 is an example of a throw-out member. The throw-out portion 36 isdiscarded after the manufacture. The throw-out portion 36 surrounds theprinted wiring boards 31. The metallic plate 34 has a predetermined gapg between the printed wiring boards 31 and the throw-out portion 36.

As shown in FIG. 4, the joining members 37 are provided inside the gap gand are located between the throw-out portion 36 and the printed wiringboards 31. The number of joining members 37 provided is six, forexample, and extend in various directions. Each joining member 37 hasone end 37 a (FIG. 6) connected to one of the printed wiring boards 31,and another end 37 b (FIG. 6) connected to the throw-out portion 36. Thejoining members 37 permits the printed wiring boards 31 to remainconnected to the throw-out portion 36. In other words, the printedwiring boards 31 are supported by the throw-out portion 36 through theuse of the joining members 37.

Circuit components 32 are mounted on the printed wiring boards 31 in thestate where the printed wiring boards 31 are supported by the throw-outportion 36. After the circuit components 32 are mounted, the joiningmembers 37 are cut off from the printed wiring boards 31. As a result,the printed wiring boards 31 are separated from the metallic plate 34.

A press working apparatus 40 according to the first embodiment of thepresent invention will now be described, referring to FIGS. 5-7. Thepress working apparatus 40 is a working apparatus that separates thejoining members 37 from the printed wiring boards 31.

FIG. 5 schematically shows the entire press working apparatus 40. Thepress working apparatus 40 includes a die assembly 41, a frame 42, a bed43 and a slide 44. The die assembly 41 includes a die 45, a blank holder46 and punches 47.

The bed 43 is fixed to the frame 42. The die 45 is provided on the uppersurface of the bed 43. The die 45 is provided with an attachment surface45 a on which the metallic plate 34 is mounted. The die 45 has aplurality of opening sections 51 which are open in the attachmentsurface 45 a. The opening sections 51 are equal in number to the joiningmembers 37. When the metallic plate 34 is set on the die 45, the openingsections. 51 are located under the joining members 37.

The slide 44 and the blank holder 46 are attached to the frame 42 insuch a manner that they are vertically movable. The slide 44 and theblank holder 46 can be advanced toward the bed 43 or retreated from thebed 43 by a driving source (not shown).

The blank holder 46 is located in correspondence to the die 45, and hasa plurality of through holes 52 at positions corresponding to theopening sections 51 of the die 45. The punches 47 are fixed to the slide44. The punches 47 are arranged at positions corresponding to theopening sections 51 of the die 45 and are inserted in the through holes52 of the blank holder 46. In other words, the punches 47 are equal innumber to the joining members 37, and are located above the joiningmembers 37 when the metallic plate 34 is set on the die 45.

The relationships between the die 45 and the punches 47 will now bedescribed in detail, referring to FIGS. 6 and 7.

As shown in FIGS. 6 and 7, an example of a punch 47 has a substantiallysquare cross section if taken in the horizontal direction. That is, thepunch 47 is a square pillar. The punch 47 has a first end portion 47 aand a second end portion 47 b. When the metallic plate 34 is set on thedie 45, the first end portion 47 a is located above that end 37 a of thejoining member 37 which is connected to the printed wiring board 31, andthe second end portion 47 b is located above that end 37 b of thejoining member 37 which is connected to the throw-out portion 36.

An example of an opening section 51 of the die 45 has a rectangularcross section if taken in the horizontal direction. That is, the openingsection 51 is a rectangle The opening section 51 extends in theinsertion direction of the punch 47 and has a depth greater than thelongitudinal dimension of the joining member 37. The opening section 51has an inner surface. The inner surface includes a first inner surfaceportion 51 a and a second inner surface portion 51 b.

When the punch 47 is inserted into the opening section 51, the firstinner surface portion 51 a is opposed to the first end portion 47 a, andthe second inner surface portion 51 b is opposed to the second endportion 47 b.

As shown in FIGS. 7 and 8, when the metallic plate 34 is set on the die45, the boundary 55 a between the printed wiring board 31 and thejoining member 37 is located between the first end portion 47 a of thepunch 47 and the first inner surface portion 51 a of the opening section51. When the metallic plate 34 is set on the die 45, the boundary 55 bbetween the throw-out portion 36 and the joining member 37 is locatedabove the second inner surface portion 51 b. In other words, the secondinner surface portion 51 b is located under the boundary 55 b betweenthe throw-out portion 36 and the joining member 37. Thus, the openingsection 51 extends from boundary 55 a (which is between the printedwiring board 31 and the joining member 37) to boundary 55 b (which isbetween the throw-out portion 36 and the joining member 37).

At the edge 51 c of the opening section 51, the attachment surface 45 aof the die 45 is perpendicular to the first and second inner surfaceportions 51 a and 51 b. This means that the edge 51 c of the openingsection 51 is not chamfered.

Gap S1 is formed between the first end portion 47 a of the punch 47 andthe first inner surface portion 51 a of the opening section 51. Gap S1is smaller than the thickness t of the metallic plate 34. Likewise, gapS2 is formed between the second end portion 47 b of the punch 47 and thesecond inner surface portion 51 b of the opening section 51. Gap S2 islarger than the thickness t of the metallic plate 34. In the case wherethe thickness t of the metallic plate 34 (which is a plate of stainlesssteel) is 0.050 mm, gap S1 is set at 0.005 mm and gap S2 is set at 0.100mm, for example.

As shown in FIG. 8, the through holes 52 of the blank holder 46 areslightly larger than the punches 47.

A plate material cutting method according to the present embodiment willnow be described, referring to FIGS. 6-10.

First of all, as shown in FIG. 6, the metallic plate 34 is placed on theattachment surface 45 a of the die 45. In other words, the metallicplate 34 is set on the die 45 in such a manner that the joining member37 of the metallic plate 34 is located above the opening section 51 ofthe die 45. To be more specific, as shown in FIG. 7, the boundary 55 abetween the printed wiring board 31 and the joining member 37 is locatedbetween the first end portion 47 a of the punch 47 and the first innersurface portion 51 a of the opening section 51. The boundary 55 bbetween the throw-out portion 36 and the joining member 37 is locatedabove the second inner surface portion 51 b of the opening section 51.

As shown in FIG. 8, after the metallic plate 34 is set on the die 45,the blank holder 46 is set at the intended position. In other words, theblank holder 46 is brought into contact with the metallic plate 34 fromabove, and the metallic plate 34 is applied with a load acting downward.Thus, the metallic plate 34 is sandwiched between the blank holder 46and the die 45, and is therefore fixed in position.

As shown in FIG. 9, after the metallic plate 34 is fixed in position,the punch 47 is forcibly pushed against the joining member 37. Themetallic plate 34 is located between the punch 47 and the die 45. Whenthe punch 47 touches the metallic plate 34, a shearing force is appliedto that portion of the metallic plate 34 which is sandwiched between thefirst end portion 47 a of the punch 47 and the first inner surfaceportion 51 a of the opening section 51. As a result, the shearing forceis exerted on the boundary 55 a between the printed wiring board 31 andthe joining member 37, and the printed wiring board 31 and the joiningmember 37 separate from each other.

Of the portions of the metallic plate 34, the portion between the secondend portion 47 b of the punch 47 and the second inner surface portion 51b of the opening section 51 is not applied with a shearing forcesufficiently strong for cutting. In general, a shearing force isgenerated when the gap between two blades is smaller than the thicknessof a workpiece. In the present embodiment, the second end portion 47 bof the punch 47 corresponds to one blade, and the second inner surfaceportion 51 b of the opening section 51 corresponds to the other. Gap S2between them is larger than thickness t of the metallic plate 34. As canbe seen from this, the boundary 55 b between the throw-out portion 36and the joining member 37 is not cut. In other words, the joining member37 is not separated from the throw-out portion 36.

The metallic plate 34 is flexible. As shown in FIG. 9, when the punch 47is inserted into the opening section 51, the joining member 37 is bentwith its end 37 b supported by the throw-out portion 36.

After being inserted into the opening section 51, the punch 47 isretreated to the original position, which is located above the metallicplate 34. As shown in FIG. 10, when the punch 47 is retreated to theoriginal position, the joining member 37 is cut off from the printedwiring board 31 but remains connected to the throw-out portion 36.

After the joining member 37 is cut off from the printed wiring board 31,the blank holder 46 is moved away from the die 45. Thus, the printedwiring board 31, which has been fixed by the die 45 until then, can betaken out. In addition, the joining member 37 and the throw-out portion36 can be taken out of the die 45 as one piece. In this way, the printedwiring board 31 can be separated from the throw-out portion 36.

The above-mentioned plate material cutting method and the die assembly41 are advantageous in that the printed wiring board 31 can be separatedfrom the throw-out portion 36 without producing cutting chips. To bespecific, a shearing force sufficiently strong for cutting is notapplied to the boundary 55 b between the throw-out portion 36 and thejoining member 37 because gap S2 between the second end portion 47 b ofthe punch 47 and the second inner surface portion 51 b of the openingsection 51 is greater than thickness t of the metallic plate 34.

Even when the punch 47 is pushed into the die 45, the joining member 37is not cut off from the throw-out portion 36, and they are integral witheach other. When the throw-out portion 36 is taken out, the joiningmember 37 is also taken out together with the throw-out portion 36.Therefore, the joining member 37 does not produce cutting chips.

Since the joining member 37 does not produce cutting chips, it does notadhere to the surface of the punch 47, blank holder 46 or die 45, andthe product does not have an indentation resulting from the joiningmember 37. In addition, the die assembly 41 need not be cleaned afterthe joining member 37 is cut off. The elimination of the need to performthe cleaning operation contributes to improvement of the manufacturingprocess of the printed circuit board 28. That is, the printed circuitboard 28 can be manufactured in a short time and at low cost.

In the case where the second inner surface portion 51 b of the openingsection 51 is under the boundary 55 b between the throw-out portion 36and the joining member 37, the joining member 37 can be bentsatisfactorily in appearance. Even if the opening section 51 is formedin such a manner that the second inner surface portion 51 b is locatedunder the throw-out portion 36, the joining member 37 can be bent by thepushing of the punch 47.

When the joining member 37 is bent, part of the throw-out portion 36 isalso subject to the bending force, and in some cases, part of thethrow-out portion 36 may crack or have another type of damage.

In the case where the second inner surface portion 51 b is under theboundary 55 b between the throw-out portion 36 and the joining member37, the throw-out portion 36 is not subject to a bending force when thejoining member 37 is bent. Therefore, the throw-out portion 36 is notdamaged.

In the case where the boundary 55 a between the printed wiring board 31and the joining member 37 is between the first end portion 47 a and thefirst inner surface portion 51 a, the cut surface is limited to theboundary 55 a between the printed wiring board 31 and the joining member37. In other words, after the cutting process, part of the joiningmember 37 does not remain attached to the printed wiring board 31.

In the case where the depth of the opening section 51 is greater thanthe longitudinal dimension of the joining member 37, the joining member37 can be freely bent in accordance with the movement of the punch 47.

In the die assembly 41, the attachment surface 45 a of the die 45 areperpendicular to the inner surface portions 51 a and 51 b. This meansthat the edge 51 c of the opening section 51 is not chamfered. Gap S2 isprovided between the second end portion 47 b of the punch 47 and thesecond inner surface portion 51 b of the opening section 51. With thisstructure, no special measure has to be taken for the edge 51 c of theopening section 51, and yet cutting chips are not produced. The die 41can be manufactured at low cost with no need to chamfer the opening edge51 c or take another special measure.

The printed circuit board 28 of the above structure is advantageous inthat it can be manufactured in a short time and at low cost. Where theprinted circuit board 28 is incorporated in the HDD 8 or the cellularphone 1, the HDD 8 or the cellular phone 1 can be manufactured in ashort time and at low cost.

A die assembly 61 and a plate material cutting method according to thesecond embodiment of the present invention will now be described withreference to FIGS. 11 and 12. The structural components that have thesame function as the die assembly 41 and printed circuit board 28 of thefirst embodiment are denoted by the same reference numerals, andreference to such structural components will be omitted herein.

As shown in FIGS. 11 and 12, the die 45 of the die assembly 61 has anopening section 62. An example of this opening section has an ellipsecross section if taken in the horizontal direction. The elliptic openingsection 62 has a long axis extending from the first inner surfaceportion 51 a to the second inner surface portion 51 b. The openingsection 62 extends from the boundary 55 a between the printed wiringboard 31 and the joining member 37 to the boundary 55 b between thethrow-out portion 36 and the joining member 37. Another example ofopening section 62 is a circle.

The die assembly 61 has a punch 63. An example of this punch has acircular cross section if taken in the horizontal direction. That is,the punch 63 is cylindrical. Gap S1 is formed between the first endportion 47 a of the punch 63 and the first inner surface portion 51 a ofthe opening section 62. Gap S1 is smaller than the thickness t of themetallic plate 34. Likewise, Gap S2 is formed between the second endportion 47 b of the punch 63 and the second inner surface portion 51 bof the opening section 62. Gap S2 is larger than the thickness t of themetallic plate 34.

The elliptic opening section 62 has the long axis extending in adirection from the first end portion 47 a to the second end portion 47b. As shown in FIG. 12 when the metallic plate 34 is set on the die 45,the boundary 55 a between the printed wiring board 31 and the joiningmember 37 is located between the first end portion 47 a of the punch 47and the first inner surface portion 51 a of the opening section 51. Whenthe metallic plate 34 is set on the die 45, the boundary 55 b betweenthe throw-out portion 36 and the joining member 37 is located above thesecond inner surface portion 51 b.

The opening section 62 extends in the insertion direction of the punch63 and has a depth greater than the longitudinal dimension of thejoining member 37. At the edge 51 c of the opening section 62, theattachment surface 45 a of the die 45 is perpendicular to the first andsecond inner surface portions 51 a and 51 b.

The printed wiring board 31 obtained by the die assembly 61 and platematerial cutting method according to the second embodiment of thepresent invention is incorporated in the cellular phone 1 or HDD 8.

The above-mentioned plate material cutting method and the die assembly61 are advantageous in that the printed wiring board 31 can be separatedfrom the throw-out portion 36 without producing cutting chips. For thesame reason as stated in connection with the first embodiment, when thepunch 63 is pushed against the throw-out portion 36, the joining member37 is cut off from the printed wiring board 31 but remains connected tothe throw-out portion 36. Therefore, the joining member 37 does notproduce any cutting chips.

The punch 63 of the second embodiment has a circular cross section. Thejoining member 37 of the metallic plate 34 is very small, and itslongitudinal dimension is several mm or less. Therefore, the punch 63 isalso very small in size and cannot be made with ease unless it iscylindrical. Compared to a rectangular cylinder, a circular cylinder iseasy to make. This holds true for the punch 63 of the second embodiment.

Since the punch 63 is cylindrical, the metallic plate 34 is cut in sucha manner as to leave an arcuate cut section. With this structure, thelength by which a edge of the punch 63 comes into contact with the platematerial 34 is large. Compared to the case where the cutting section isflat, the cutting line of the arcuate cutting section is sufficientlylong. As a result, a reliable cutting operation is ensured.

A description was given above of the plate material cutting methods anddie assemblies of the first and second embodiments of the presentinvention, along with printed circuit board 28 and cellular phone 1.Needless to say, the embodiments of the present invention are notlimited to these. For example, the opening sections 51, 62 may havecross sections other than rectangular and oval ones. In addition, theopening sections 51, 62 need not extend from the boundary 55 a betweenthe printed wiring board 31 and the joining member 37 to the boundary 55b between the throw-out portion 36 and the joining member 37.

For example, the second inner surface portion 51 b of the openingsection 51 may be at any position as long as it is located under thejoining member 37. In other words, the opening section 51 is formed insuch a manner that the first inner surface portion 51 a is at a positioncorresponding to the plate material portion to be cut. As long as thefirst inner surface portion 51 a is located at such a position, thesecond inner surface portion 51 b does not have to be at a specificposition. As in the opening sections 51 and 62 of the first and secondembodiments, however, it is effective that the second inner surfaceportion 51 b be located close to the throw-out portion 36. Where thesecond inner surface portion 51 b is close to the throw-out portion 36,the opening sections 51 and 62 can have a wide cross section, and theopening sections 51 and 62 can be formed with ease. As shown in FIG. 13,the opening edge 51 c of the opening section 51 may be chamfered so thatthe joining member 37 can be easily bent.

The printed circuit board to which an embodiment of the presentinvention is applied is not limited to that adapted for use in the HDD8, and is applicable to any type of electronic apparatus. Moreover, theembodiments of the present invention are not limited to the printedcircuit board 28. For example, the embodiments of the present inventionare applicable to the case where a plate made of a material other than ametal (such as resin or rubber) is cut. The embodiments of the presentinvention are applicable to any type of plate material on condition thatthe plate material does not break when it is bent.

While certain embodiments of the inventions have been described, theseembodiments have been presented by way of example only, and are notintended to limit the scope of the inventions. Indeed, the novel methodsand systems described herein may be embodied in a variety of otherforms; furthermore, various omissions, substitutions and changes in theform of the methods and systems described herein may be made withoutdeparting from the spirit of the inventions. The accompanying claims andtheir equivalents are intended to cover such forms or modifications aswould fall within the scope and spirit of the inventions.

1. A plate material cutting method comprising: preparing a platematerial including a main body portion, a throw-out portion and ajoining member that joins the main body portion to the throw-outportion; setting the plate material on a die including an openingsection such that the joining member is opposed to the opening section;and pushing a punch opposing the opening section against the joiningmember, the punch including a first end portion corresponding to a firstend of the joining member which is connected to the main body portion, agap smaller than thickness of the plate material being defined betweenthe first end portion of the punch and an inner surface of the openingsection, the punch also including a second end portion corresponding toa second end of the joining member which is connected to the throw-outportion, a gap larger than the thickness of the plate material beingdefined between the second end portion of the punch and the innersurface of the opening section.
 2. The plate material cutting methodaccording to claim 1, wherein the punch is cylindrical, and the openingsection of the die is ellipse having a long axis extending in adirection from the first end portion to the second end portion.
 3. Theplate material cutting method according to claim 1, wherein the innersurface of the opening section includes a first inner surface portioncorresponding to the first end portion of the punch and a second innersurface portion corresponding to the second end portion of the punch,and the second inner surface portion is located under a boundary betweenthe throw-out portion and the joining member when the plate material isset on the die.
 4. The plate material cutting method according to claim3, wherein a boundary between the main body portion and the joiningmember is located between the first end portion of the punch and thefirst inner surface portion of the opening section when the platematerial is set on the die.
 5. The plate material cutting methodaccording to claim 4, wherein the punch is cylindrical, and the openingsection of the die is ellipse having a long axis extending in adirection from the first end portion to the second end portion.
 6. Theplate material cutting method according to claim 4, wherein the openingsection of the die extends in a direction in which the punch isinserted, and has a depth greater than a longitudinal dimension of thejoining member.
 7. The plate material cutting method according to claim6, wherein the die includes an attachment surface on which the platematerial is placed, and the attachment surface is perpendicular to thefirst and second inner surface portions of the opening section at anopening edge of the opening section.
 8. A printed circuit boardcomprising: a main body portion prepared from a plate material by use ofa punch and a die including an opening section corresponding to thepunch, the plate material including the main body portion, a throw-outportion and a joining member that joins the main body portion to thethrow-out portion; and a circuit component mounted on the main bodyportion, wherein the punch includes a first end portion and a second endportion, when the plate material is set on the die, the first endportion of the punch corresponds to a first end of the joining memberwhich is connected to the main body portion, the second end portion ofthe punch corresponds to a second end of the joining member which isconnected to the throw-out portion, a gap smaller than thickness of theplate material is defined between the first end portion of the punch andan inner surface of the opening section, and a gap larger than thethickness of the plate material is defined between the second endportion of the punch and the inner surface of the opening section. 9.The printed circuit board according to claim 8, wherein the punch iscylindrical, and the opening section of the die is ellipse having a longaxis extending in a direction from the first end portion to the secondend portion.
 10. The printed circuit board according to claim 8, whereinthe inner surface of the opening section includes a first inner surfaceportion corresponding to the first end portion of the punch and a secondinner surface portion corresponding to the second end portion of thepunch, and the second inner surface portion is to be located under aboundary between the throw-out portion and the joining member.
 11. Theprinted circuit board according to claim 10, wherein a boundary betweenthe main body portion and the joining member is to be located betweenthe first end portion of the punch and the first inner surface portionof the opening section.
 12. An electronic device comprising: a casing;and a printed circuit board received in the casing, the printed circuitboard including a main body portion and a circuit component mounted onthe main body portion, wherein the main body portion is prepared from aplate material by use of a punch and a die including an opening sectioncorresponding to the punch, the plate material includes the main bodyportion, a throw-out portion and a joining member that joins the mainbody portion to the throw-out portion, the punch includes a first endportion and a second end portion, when the plate material is set on thedie, the first end portion of the punch corresponds to a first end ofthe joining member which is connected to the main body portion, and thesecond end portion of the punch corresponds to a second end of thejoining member which is connected to the throw-out portion, a gapsmaller than thickness of the plate material is defined between thefirst end portion of the punch and an inner surface of the openingsection, a gap larger than the thickness of the plate material isdefined between the second end portion of the punch and the innersurface of the opening section.
 13. The electronic device according toclaim 12, wherein the punch is cylindrical, and the opening section ofthe die is ellipse having a long axis extending in a direction from thefirst end portion to the second end portion.
 14. The electronic deviceaccording to claim 12, wherein the inner surface of the opening sectionincludes a first inner surface portion corresponding to the first endportion of the punch and a second inner surface portion corresponding tothe second end portion of the punch, and the second inner surfaceportion is to be located under a boundary between the throw-out portionand the joining member.
 15. The electronic device according to claim 14,wherein a boundary between the main body portion and the joining memberis to be located between the first end portion of the punch and thefirst inner surface portion of the opening section.